With a known drilling tool of this type as disclosed in U.S. Pat. No. 4,875,531 for drilling pilot cores, the deep well drilling motor to drive the core barrel of the core drilling unit is designed as a Moineau motor and is a retractable part of the core drilling unit. The stator of the deep well drilling motor is supported so it can move axially but cannot rotate in the longitudinal guides of the outer casing, and the core barrel of the core drilling unit is rotationally mounted in the lower end area of the stator of the deep well drilling motor and is connected to the output shaft of the deep drilling motor. A similar drilling tool is described in U.S. Pat. No. 4,518,050, where a turbine that forms a component of the retractable core drilling unit is provided as the drilling motor.